Production of alkylhoalosilanes



Patented May 10, 1949 PRODUCTION OF ALKYLHALOSILANES Lee De Pree, Holland, and Arthur J. Barry and Donald E. Hook, Midland, Micln, aasignora to The Dow Chemical Company, Midland, Mich., a corporation oi Delaware No Drawing. Application November 13, 1946, Serial No. 709,422

9 Claims. 1

This invention relates to the preparation of alkylhalosilanes. It is particularly concerned with a new reaction between an alkyl halide and a compound of silicon containing both hydrogen 2 tribromosilane, HSiBra, dichlorolnonofluorosilane, HSiFClz, monobromodlchlorosilane, HSiBrCla, etc., may be employed if desired.

Suitable alkyl halides include monochloro and and halogen attached directly to the silicon atom. 5 monobromo-substituted alkanes containing a plu- Briefly, we have found that an alkyl halide in rality of carbon atoms in the molecule, such as which the alkyl radical contains a plurality of ethyl chloride, propyl bromide, n-butyl chloride, carbon atoms may be caused to react with an inn-butyl bromide, isobutyl chloride, decyl chloorganic compound of silicon which contains at ride, decyl bromide, dodecyl chloride, octadecyl least one hydrogen atom and at least one halogen chloride, etc. atom attached directly to the silicon atom, e, g. Commercial grades of the starting materials HSiCls, at a temperature of 400 C. or below, by may be employed, but impurities present in reactconducting the reaction at an elevated pressure, ants of technical quality sometimes take part in for instance a pressure above 100 pounds, and side reactions which consume a portion of the usually in the order of from 200 to 2500 pounds, halosilane, with resultant reduction in the yield per square inch, or higher. The products of reof the desired product. Because of the fact that action comprise the corresponding alkylhalosilane the reaction products are hydrolyzable, it is imand an inorganic halosilane more highly haloportant that the reaction be carried out under genated than the starting material. Minor substantially anhydrous conditions. amounts of a saturated hydrocarbon, hydrogen, The preferred mode of practicing the invention a hydrogen halide, etc. are formed as by-prodinvolves heating a mixture of the alkyl halide and ucts. For example, when a mixture of ethyl chloan inorganic trihalosilane in a suitable reaction ride and trichlorosilane is heated in a closed sysvessel, e. g. a bomb or autoclave. Usually from tem, there is produced for the most part ethyl- 0.5 to 3.0 molar equivalents of trihalosilane are trichlorosilane and silicon tetrachloride, together as employed for each molar equivalent 'of alkyl halwith smaller quantities of ethane and hydrogen. ide. It is sometimes advantageous to employ a Apparently, the rate and efliciency of the reacsolvent, e. g. a saturated fraction of petroleum, tion are dependent to a large extent upon the which is substantially inert under the reaction proximity of the molecules to be reacted. Emconditions, to insure mutual solution of the startployment of a pressure suflicient to liquefy a poring, materials. The reaction products and any tion of the reaction mixture results in rapid reunreacted materials are withdrawn from the reaction at a lower temperature than when the mixactor and purified, e. g. by fractional distillation. ture is entirely in the vapor phase. The pressure Unreacted components may be returned to stock which may most advantageously be employed defor further processing. The reaction may be carpends, of course, upon the starting materials, but ried out batchwise or in continuous manner, e, g. in general lies within the range stated above. The by passing a stream of the reaction mixture under pressure may be developed autogenously within a pressure through a heated tubular autoclave. system or may be superimposed by means of a The following examples illustrate certain ways pump or by developmentof a hydrostatic presin which the principle of the invention has been sure, applied, but are not to be construed as limiting The reaction may be carried out satisfactorily the invention: at temperatures below 400 C., e. g. between 250 Example 1 and 400 C., the optimum temperature depending to some extent upon the pressure. Heating t One gram molecular equivalent weight of ethyl system at higher tfimperaturesi abOVe chloride and one gram mol of trichlorosilane were usually results 111 the Production of complex charged into a nickel bomb of 500 milliliter camixtures, probably due to decomposition of pripacjty The sealed bomb was heated to a mary products, occurrence of side reactions, etc. perature of 2 (3" measured by a they- AS has e ed P o 1131051181195 mocouple in a thermocouple well of the bomb. which may be satisfactorily employed under the During heating, the maximum pressure attained conditions of this invention are inorganic comwithin th system was approximately 1800 pounds pounds of silicon containing at least one hydroper square inch. Heating was continued for 22 gen atom and at least one halogen atom attached hours, after which the bomb was cooled and directly to the single silicon atom of the molecule. vented through condensers. The condensate was subsequently fractionally distilled. There were We prefer to use trichlorosilane, HSiCla, although obtained 0.21 gram mol of ethyltrichlorosilane and 0.66 gram mol of silicon tetrachloride.

In another experiment, the bomb was charged with 0.5 gram mol of ethyl chloride and one gram mol of trichlorosilane, and heated at 263-282 C.

for 16 hours. There were obtained 0.11 gram mol of ethyltrichlorosilane and 0.52 gram mol of silicon tetrachloride.

In both experiments unreacted trichlorosilane was also recovered.

Example 2 recovered.

Example 3 A bomb charged with 0.5 gram molecular weight of n-butyl chloride and 0.5 gram mol of trichlorosilane was heated at 263-284 C. for 16 hours, and the reaction products collected as in the preceding examples. There was obtained approximately 0.12 gram mol of a product distilling at 144.5-150 C. at 740 millimeters absolute pressure, and consisting of a mixture of normaland secondary-butyltrichlorosilanes. About 0.32 gram mol of silicon tetrachloride was also obtained.

The experiment was repeated, employing isobutyl chloride as a reactant. Approximately 0.17 gram mol of butyltrichlorosilane, distilling principally at 140.5-l45 C., and consisting chiefly of isobutyltrichlorosilane was obtained, together with 0.21 gram mol of silicon tetrachloride. Unreacted trichlorosilane was also recovered.

Example 4 By procedure similar to that described in the preceding examples, a mixture of higher alkyl chlorides (prepared from Lorol, i. e. technical lauryl alcohol) was reacted with trichlorosilane in a bomb. The product comprised a mixture of higher alkyltrichlorosilanes, distilling at temperatures between 104 and 195C. at 12-13 millimeters absolute pressure, and also silicon tetrachloride and unreacted trichlorosilane.

Operating in a manner similar to that described in the examples given above, ethyl bromide and tribromosilane may be reacted to produce ethyltribromosilane; propyl bromide and tribromosilane may be reacted to produce propyl tribromosilane; butyl bromide may be reacted with tribromosilane to give butyltribromosilane, decyl bromide and tribromosilane may be reacted to give decyl tribromosilane; octadecyl bromide may be reacted with tribromosilane to produce octa- -decy1 tribromosilane; etc.

We therefore point out and distinctly claim:

1. The process which comprises reacting an alkyl halide, in which the alkyl radical contains a plurality of carbon atoms, with an inorganic halosilane consisting of hydrogen, halogen, and silicon atoms and having both hydrogen and halogen atoms attached directly to the silicon atom, at a pressure of at least 100 pounds per square inch and a temperature between 250 and 400 C. to form an alkylhalosilane. I

2. A process for the preparation of an alkylhalosilane which comprises reacting an alkyl halide, in which the alkyl radical contains a plurality of carbon atoms, with an inorganic halosilane consisting of hydrogen, halogen, and silicon atoms and having both hydrogen and halogen atoms attached directly to the silicon atom at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch.

3. A processfor the preparation of an alkyltrihalosilane which comprises reacting an alkyl halide, containing a plurality of carbon atoms in the alkyl radical, with a trihalosilane, having the halogen atoms and a hydrogen atom attached to a silicon atom, at a temperature between 250 and 400 C. and a pressure of at least100 pounds per square inch.

4. A process for the preparation of an alkyltrichlorosilane which comprises reacting an alkyl halide, containing a plurality of carbon atoms in the alkyl radical, with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least pounds per square inch.

5. A process for the preparation of an alkyltrichlorosilane which comprises reacting an alkyl chloride, containing a plurality of carbon atoms in the alkyl radical, with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch.

6. A process for the preparation of an alkyltrichlorosilane which comprises reacting an alkyl chloride, containing from 2 to 18 carbon atoms in the alkyl radical, with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch.

7. The process for the preparation of ethyltrichlorosilane which comprises reacting ethyl chloride with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch.

8. The process for the preparation of propyltrichlorosilane which comprises reacting propyl chloride with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch- 9. The process for the preparation of lauryl trichlorosilane which comprises reacting lauryl chloride with trichlorosilane at a temperature between 250 and 400 C. and a pressure of at least 100 pounds per square inch. I

LEE DE PREE. ARTHUR J. BARRY. DONALD E. HOOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,379,821 Miller July 3, 1945 2,407,181

Scott Sept. 3, 1946 

